1. Field of the Invention
The present invention relates to lifting device, and more particularly to a lifting device of a treadmill for folding the structure of the treadmill.
2. Description of Related Art
A conventional lifting device of a treadmill in accordance with the prior art shown in FIGS. 8 and 9 comprises base member (5) and a U-shaped connector (63) secured on a front portion of the base member (5). A main frame (6) is pivotally connected to two free ends of the U-shaped connector (62). A first motor (61) is mounted to the main frame (6) for driving an endless strap (62) that is mounted around the main frame (6). A linear driver (7) is mounted to a bottom of the main frame (6) and includes a telescopic rod (72) that is driven by a second motor (not shown). The telescopic rod (72) has a first end secured on the bottom of the main frame (6) and a second pivotally connected to a lift arm (8) that includes two opposite ends respectively pivotally connected to two opposite sides of the U-shaped connector (63). Two supports (not numbered) respectively extending from two opposite ends of the lift arm (8) and each having a roller (81) rotatably mounted on the free end thereof. The two rollers (81) are adapted to abut a supporting surface for lifting the front portion of the main frame (6). For folding the treadmill, the user only needs to directly lift the rear portion of the main frame (6) to make the two rollers (81) backward move over the gravity of the main frame (6) for reducing the volume of the treadmill during being stored.
To fold the treadmill with the conventional lifting device is a laborious work because the convention lifting device of a treadmill without auxiliary structure for effort-saving. However, the main frame of a treadmill is a very heavy element for children or weak user to lift.
There is no fastener for positioning the lifted main frame (6). The lifted main frame (6) may fall down and crash the supporting surface due to a sudden bump. Furthermore, the falling main frame (6) may hurt the user. It is very dangerous.
The length of the telescopic rod (72) is used to limit the position of the lift arm (8) when lifting the main frame (6) and the first end of the telescopic rod (72) is pivotally mounted on the bottom of the main frame (6) so that all the gravity of the main frame (6) focus on the pivotal portion between the telescopic rod (72) and the lift arm (6). As a result, the pivotal portion between the telescopic rod (72) and the lift arm (6) may be broken after the treadmill being used for a period of time.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional lifting device of a treadmill.